Peng, H.-J. | bioRxiv Science

bioRxiv2023

Avirulent ME49Δgra5 Protecting Hosts Against Toxoplasma gondii Infection and Breast Tumors

Toxoplasma gondii is the causative agent of toxoplasmosis, a zoonotic disease that poses a threat to human health and a considerable loss to livestock farming. At present, clinical therapeutic drugs mainly target T. gondii tachyzoites and fail to eradicate bradyzoites. Developing a safe and effective vaccine against toxoplasmosis is urgent and important. T. gondii possesses dense granule organelles that secrete immunogenic dense granule proteins (GRAs). GRA5 localizes to the parasitophorous vacuole membrane (PVM) in the tachyzoite stage and to the cyst wall in the bradyzoite stage. Here we report that gra5 knockout T. gondii strain is avirulent and fails to form cysts, but stimulates sero-conversion in mice. We next investigated the protective efficacy of ME49{Delta}gra5 vaccination against T. gondii infection. All the immunized mice survived the challenge infection with either wild-type RH, ME49, VEG tachyzoites or ME49 cysts. Remarkably, ME49{Delta}gra5 tachyzoites inoculation in situ attenuated the growth of murine breast tumor (4T1) in mice and prevented 4T1s lung metastasis. ME49{Delta}gra5 inoculation might upregulate the levels of Th1 cytokines and tumor-infiltrating T cells in tumor microenvironment (TME) and trigger anti-tumor responses by increasing the number of NK, B, T cells, macrophages, and dendritic cells (DCs) in spleen. Collectively, the results support the potential of ME49{Delta}gra5 as attenuated live vaccine against T. gondii infection and breast cancer. Author summaryThe zoonotic toxoplasmosis poses a great disease burden to humans and big loss to livestock farming. At present, clinical therapeutic drugs mainly target T. gondii tachyzoites but have no effect on bradyzoites. A safe and effective vaccine against toxoplasmosis is urgent and important. Dense granule proteins (GRAs) are a group of immunoactive proteins secreted by T. gondii dense granule organelles. GRA5 is located on the parasitophorous vacuole membrane (PVM) at the tachyzoite stage and on the cyst wall at the bradyzoite stage. We discovered that the gra5 knockout T. gondii strain became avirulent and failed to form cysts in mice. ME49{Delta}gra5 immunized mice survived the challenge infection of wild-type RH, ME49, and VEG tachyzoites, and ME49 cysts. Meanwhile, ME49{Delta}gra5 tachyzoites inoculation in situ remarkably attenuated the growth of murine breast tumor (4T1) in mice including the injected and distant tumors, as well as prevented 4T1s lung metastasis. This results support the potential of ME49{Delta}gra5 as attenuated live vaccine against T. gondii infection and breast cancer.

microbiology↗

bioRxiv2018

Toxoplasma gondii ROP18 Inhibits Human Glioblastoma Cell Apoptosis through Mitochondrial Pathway by Targeting Host Cell P2X1

It is known that Toxoplasma gondii infection both initiates and inhibits host cell apoptosis through different proapoptotic signaling cascades, but the parasitic factors involved in these processes remain unclear. T. gondii virulence factor ROP18 has been reported to regulate host cell apoptosis, but the results of this regulation are few reported and contradictory. In this study, we found that immune or neuro cells infected by any one of the T. gondii strains (RH-type I, ME49-type II, and VEG-type III) showed a significantly lower apoptosis index than their uninfected controls when apoptosis was induced by staurosporine (STS). We further found that ROP18 of RH strain inhibited ATP induced apoptosis in human glioblastoma cells (SF268) with endogenous expression of human proapoptotic protein purinergic receptor 1 (P2X1), but had no effects on the immune cells of RAW264.7 and THP-1 without detectable P2X1 expression, which may indicate that ROP18s inhibition of host cell apoptosis is related to P2X1. Interestingly, we further identified that ROP18 (RH strain) interacted with P2X1, and over-expression of ROP18 in COS-7 cells inhibited the cell apoptosis mediated by P2X1. We also found that ROP18 of RH strain inhibited P2X1-mediated Ca2+ influx, translocation of cytochrome C from mitochondria to cytoplasm, and 1 ATP-triggered caspases activation. Collectively, these findings supported that ROP18 inhibited the host cell apoptosis through the intrinsic mitochondria pathway by targeting host cell P2X1, thereby suggesting a sensor role of the host proapoptotic protein P2X1 in this process\n\nAuthor summaryThe obligate intracellular protozoan Toxoplasma gondii has been shown to modulate cell apoptosis through different apoptotic pathways. However, the consequences are various and even contradictory, and the parasite effectors and the precise biological mechanisms remain unclear. Herein we showed that T. gondii of type I, II, and III strains could inhibit the apoptosis of neuro cells and immune cells. Toxoplasma gondii ROP18 (RH strain) inhibited apoptosis of human glioblastoma cell SF268 by targeting C terminal of host cell P2X1 protein, but not through proteasome-dependent degradation of P2X1.

molecular biology↗